How to Check Memory Usage on Ubuntu
There are times when computer users experience situations where the system suddenly becomes slow or applications unexpectedly terminate.
One of the possible causes of such behavior is an issue related to memory usage.
Memory is a component that temporarily stores data while the operating system and applications are running.
Accurately understanding the state of memory is a fundamental task for analyzing and understanding how a system operates.
1. Why Checking Memory Usage Matters
Monitoring memory usage helps users understand the current state of the system and how resources are being allocated.
By checking memory usage, you can identify:
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How much memory is currently in use
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Whether the system has enough available memory
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How memory is shared between applications, buffers, and cache
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Potential memory pressure situations
These insights are useful for desktops, development environments, servers, and testing systems alike.
2. How Linux Manages Memory
Linux uses memory aggressively to improve performance.
Unused memory is often allocated to buffers and cache, which helps speed up file access and system operations.
As a result, Linux systems may appear to use a large amount of memory even when they are operating normally.
Understanding this behavior is essential to interpreting memory statistics correctly.
3. Checking Memory Usage with the free Command
The free command is one of the simplest ways to view memory usage.
To display values in a more readable format, use:
Key Output Fields
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total: Total physical memory installed
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used: Memory currently in use
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free: Memory not currently used
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buff/cache: Memory used for buffers and cache
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available: Memory that can be used by new applications
The available field is particularly important, as it represents memory that can be allocated without affecting system performance.
4. Viewing Detailed Memory Information with /proc/meminfo
Linux exposes internal system information through the /proc virtual filesystem.
Detailed memory statistics can be found here:
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| cat command |
This file provides extensive information, including:
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MemTotal
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MemFree
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MemAvailable
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Buffers
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Cached
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SwapTotal
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SwapFree
This method is commonly used by monitoring tools and automation scripts.
5. Real-Time Memory Monitoring with top
The top command displays real-time system activity.
The top section of the output shows overall memory and swap usage, while the lower section lists running processes.
Memory-Related Fields
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MiB Mem: Total, used, and free memory
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MiB Swap: Swap usage statistics
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%MEM: Percentage of memory used by each process
This view helps identify which processes are consuming the most memory.
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| top command |
6. Using htop for a Visual Overview
htop is an enhanced alternative to top, offering a more user-friendly interface.
Features of htop include:
Its graphical layout makes it easier to interpret memory usage patterns, especially for new users.
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| htop command |
7. Monitoring Memory Activity with vmstat
The vmstat command provides a snapshot of system resource activity.
Memory-related columns include:
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free: Available memory
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buff: Buffer memory
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cache: Cache memory
Running vmstat at intervals can help observe memory usage trends over time.
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| vmstat command |
8. Checking Memory Usage in a Graphical Environment
On Ubuntu desktop systems, memory usage can also be monitored using graphical tools.
The System Monitor application provides:
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Visual graphs of memory usage
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Per-process memory consumption
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Combined CPU, disk, and network information
This approach is useful for users who prefer a visual overview rather than command-line tools.
9. Understanding Swap Memory Usage
When physical memory is insufficient, Linux uses swap space, which is stored on disk.
Swap usage can be checked with:
Swap information is also displayed in the output of free -h.
Swap improves system stability by preventing memory exhaustion, although it is slower than physical memory.
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| swapon command |
10. Interpreting Memory Usage Correctly
When analyzing memory usage on Linux, it is important to keep the following points in mind:
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Cache memory is released automatically when needed
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Low “free” memory does not necessarily indicate a problem
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The “available” value provides a better picture of usable memory
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Short-term spikes in memory usage are often normal
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Long-term trends are more meaningful than single measurements
Understanding how memory values relate to one another helps avoid misinterpretation.
11. Conclusion
Checking memory usage is one of the fundamental tasks in system operation.
Linux and Ubuntu provide a variety of tools and commands that allow users to monitor memory status.
By using tools such as free, top, /proc/meminfo, and the system monitor, it is possible to clearly understand how the system is currently operating.
